WO1992016690A1

WO1992016690A1 - Process for eliminating non-flatness in the manufacture of webs, especially in cardboard machines, and device for implementing it

Info

Publication number: WO1992016690A1
Application number: PCT/EP1992/000443
Authority: WO
Inventors: Manfred Stemmer
Original assignee: Stora Feldmühle Aktiengesellschaft
Priority date: 1991-03-13
Filing date: 1992-02-29
Publication date: 1992-10-01
Also published as: ES2074880T3; ATE125014T1; DE4108056A1; DE59202877D1; EP0575371A1; EP0575371B1

Abstract

The process makes it possible continuously to adjust the actual curvature to eliminate not-flatness in the manufacture of webs, especially in cardboard machines, by means of a pressure strip arranged in front of the take-up system having a guide component in the form of a round rod and rotated by means of a rotary drive. Here, the pressure strip (3) is fitted across the direction of travel (2) of the web and is movable perpendicularly thereto. The surface dampness of the upper and lower sides of the travelling web is continuously or intermittently measured and from the difference between the measurements xe1 thus obtained is derived the setting xa1, according to which the depth of penetration of the pressure strip (3) is adjusted.

Description

Process for eliminating flatness faults in the production of webs, in particular in cardboard machines, and device for carrying them out.

The present invention relates to a method according to the preamble of claim 1, and device for its implementation with a crusher bar arranged in the machine frame, oriented transversely to the machine direction and movably mounted perpendicularly thereto.

Flatness problems occur in the case of heavier sheets of paper or cardboard in the form of curling, with the edges of a sheet not lying flat on the base. A distinction is made between the curvature of the arches on the one hand towards the bottom or top and on the other hand in the longitudinal or transverse direction. Above all, the curvature to the cover of cardboard sheets or to the side of paper sheets to be printed leads to stoppers in the further processing machines, in particular printing machines, and thus to rejects.

Especially for cardboard types with basis weights of

_2nd more than 200 g / m it should be noted that a Sets curvature in the longitudinal direction. The contribution of the tendency to curl in the upright direction, which is present in the box, is compensated for with increasing bending stiffness and does not appear or is acted upon by the curling tendency in the longitudinal direction into a desired curvature, ie a curvature towards the base.

In principle, a carton could only be produced without any significant curvature if its mechanical properties and its moisture expansion behavior would be symmetrical with respect to its neutral plane. However, this cannot be assumed in practice if almost 100% waste paper is used in cardboard production. A cardboard box made from waste paper with a top layer, intermediate layer and underlay and possibly a single or multiple stroke application has considered such an inhomogeneous composition of matter over the cross section of the cardboard box that a pronounced curling tendency is inevitable.

The specialist in cartonboard production knows many possibilities of influence today, for example in the literature: "M. Jud, operational difficulties with fine, kraft and special paper machines and their elimination, Güntter Staib-Verlag, 2nd edition, 1982." be listed. First and foremost is the difference in moisture expansion of the top and bottom surface, which can influence the size and direction of the curvature by drying or moistening. In particular, the problem that has not been overcome to date is that The curvature of the carton regarding its cause cannot be determined while the machine is running. Samples can only be taken from the reel after the web has come to a standstill, transition or tearing, and measures can be taken regarding the curvature by changing the drying capacity in the afterdry group or moistening at a suitable point on the web guide. The late availability of machine operators to influence the curvature is the reason why the main reject source is still due to the curvature of the web.

In the so-called "laboratory curvature", the maximum curvature of the long side is measured from an A4 sheet. The quality tolerance range extends e.g. from 0 = flat to + 10 mm to the base, which defines the curvature of the cardboard towards the base.

A disadvantage when the post-drying group of a board machine is heated differently is that the performance of the machine is reduced due to the theoretical drying capacity which cannot be used. The determined laboratory curvature specifies the ratio in which the vapor pressure of the upper drying cylinders to that below the drying cylinders in the after-dryer group should be set. For a given final moisture content of the web, the reduction in the total drying capacity of the after-drying group follows from the required adjustment range of the steam pressure of the drying cylinders. A very different heating of the drying cylinders also leads to Wrinkling of the cardboard web with frequent tearing due to folded web edges, especially in the inlet of a coating system operated in the ON-LINE.

The moistening of the web by means of water spray pipes has a similar, albeit less controllable influence on the curling tendency than the drying. Here, too, there is the disadvantage of a reduction in the performance of the machine, since the water applied to the curvature also has to be evaporated again in order to achieve the required final moisture content of the web. Further disadvantages of moistening with water are that the curvature effect depends on the amount of water applied and this in turn

the dependable function of the uniform spray pattern of individual nozzles and the absorbency of the web material is dependent.

The latter applies particularly to cardboard types below 200 g / m 'with the effect of increasingly bulged and cross-wave appearances from sheets cut in the cross cutter and stacked into sheets.

DE-PS 132 241 relates to a method and

Device with which the one-sided coated papers can be rolled up by breaking the coherent coating layer into small ones

Individual areas should be prevented. The reason for the curling is the shortening of the surface of the coating color after drying. The coating layer is broken down into small individual areas by rolling with a transverse and longitudinal corrugation by pulling the paper over rounded edges. A disadvantage of the proposed method is that only papers with a brittle line application, which after drying can be broken down into small individual areas by appropriate treatment, can be used. Such a massive longitudinal and transverse breaking has a disadvantageous effect on the stiffness of the paper, so that after the treatment there is a lobed paper with low stiffness. The method proposed here cannot be used with cardboard, especially with cardboard that is smooth on one side or coated cardboard, since the corrugating rollers damage the surface or top of the cardboard by permanently affecting the smoothness and gloss that was generated there, so that the cardboard in particular with so-called chromo replacement or chromo cardboard completely loses its use value.

Correction of flat position errors during the further processing of the reel is often transferred to the equipment. The curvature in the running direction of the web can be changed, for example, by inserting breaker bars, as are known from German utility model 87 13 445, within a cross cutter. This makes it possible to correct faulty paper rolls. The breaker effect, ie the reduction of tension on one side of the web, is achieved by pulling the web under tension over the sliding surface of the breaker bar provided with a small radius. The immersion depth of the crusher line is perpendicular to the web running direction and is determined according to the respectively determined one Laboratory curvature controlled. The principle of operation of the crusher line known from DE-GM 87 13 445 is unsuitable for use in the online operation of a board machine. Disadvantages arise from the large amount of heat generated on the sliding surface, the increased wear on the sliding surfaces and the abrasion of the underside of the carton with corresponding dusting.

The correction of flat position errors in the equipment has the following disadvantages:

a) The productivity of the paper processing machines is reduced. For every change in the laboratory curvature outside the

Countermeasures take place. For example, the setting depth of a crusher bar must be included in the cross cutter

Multiple processing, for each newly listed web, be adjusted several times until the curvature is within the quality tolerance range, whereby the reject rate increases and the profitability of the machine decreases.

b) Any fluctuations in the curvature of the web during the running time of a reel cannot be recorded directly. Here, too, a retrospective adjustment with a corresponding reject rate must be made from the finished product.

c) The work share of the staff in quality assurance in the area of equipment increases significantly. Still, a gapless Detection of flatness of individual sheets in a pallet can hardly be achieved. The result is an increase in customer complaints, primarily due to sheet transport problems in the printing press.

The object of the invention is to provide a method which has a continuous influence on the curvature is value for eliminating flatness disturbances in the production of webs, in particular in board machines with current web speeds, for example one

Web speed of 450 m / min. with a basis weight of the cardboard of 220 g / m _>, whereby once a "target laboratory curvature" can be kept stable with a regulation over a period of several hours and the drying performance of the drying group can only be used for web drying and that, furthermore, none due to the procedure

Loss of bending stiffness of the web material occurs.

Another object of the invention is to improve a device known as a breaker bar for mechanically eliminating flatness disturbances in such a way that the device can be operated without problems in the cardboard machine and any formation of dust on the web is largely avoided or dust that is created can be removed immediately .

The measurements carried out over a longer period of time on cardboard webs on one of the practical ones Cardboard machine running under conditions has shown that an increase in the difference in surface moisture relative to each other means more curvature to the ceiling, and surprisingly it does not matter whether the total moisture of the web is at a low or high level, that is to say the fluctuations in the total moisture have no effect on the curvature , the only difference is the difference in surface moisture. It is not decisive which individual factors affect the surface moisture, e.g. B. the ceiling, such as degree of grinding, pH, basis weight, retention, fabric and chemical formulation, ash content of the ceiling, etc., influence. The same applies to the base and its surface moisture.

Based on this finding, the present invention proposes to solve the problem in one

Method according to the generic term of claim

1 before that a shaped as a round bar and means

Rotary drive rotated guide element acts perpendicular to the web running direction on the underside of the web, such that to control the flatness of a

Cardboard sheet the manipulated variable for the immersion depth of the

Guide element in the underside of the web from the difference of the continuously or intermittently measured

Surface moisture of the running web and

The underside of the web is derived, so that when the surface moisture difference changes, the immersion depth of the

Guide element, which is indicated by position sensors, is adjusted accordingly. Advantageous embodiments of the method are specified in subclaims 2 to 5.

The combination of the features according to the invention results in a control loop, the difference between the

Surface damp blanket to underlay, for example a cardboard box, serves as the standard actual value. The

Actuator here is a guide element acting on the underside of the web, which with two in

Diameter of relatively large guide rollers causes a three-fold change in direction of the web, d. H. the wrap angle of the web increases due to the

Geometry approximately proportional to the immersion depth of the guide element. So there is a mechanical one

Actuator available with which a change of the

Actual curvature value can be done without any special

To have to take measures for example during drying. The surface moisture difference that changes during the production process specifies how far the current position sensor indicates

Immersion depth of the guide element must be changed to finally bring about the required change in curvature. The new immersion depth to be controlled

Guide element can be done manually, for which purpose then as

Position indicator an optical display of the

Immersion depth is sufficient. This is preferably done

Positioning of the guide element automatically, for which purpose a position transducer, for example an inductive displacement transducer, for monitoring and feedback of the current immersion depth of the

Leitelementeε is required. In the method according to the invention, the performance capacity of a board machine could be increased by up to 10% without the curvature determined on the reel samples deviating from the specified quality tolerance range. In addition, it was found that a wrap angle of the web achieved by the immersion depth of the guide element over the guide element up to 60 degrees has no influence on the bending stiffness required for the cardboard, as shown in Example 2 below for differently heavy cardboard materials.

In the method according to the invention, it had been found to be particularly advantageous to have the guide element rotate in the direction of web travel or in opposite directions, the peripheral speed of the guide element being chosen to be less than 1% of the web speed. The rotation of the ^* s guide element reduces friction and prevents tearing out of track components, which can lead to the dreaded dusting. In addition, one-sided wear of the same is prevented by the rotation of the guide element.

In a further advantageous embodiment of the invention, the guide element is cooled. The guide element can be cooled by means of water or air.

The measurement of the surface moisture, which is independent of a basis weight measurement, has proven to be accurate

Infrared reflection sensor measurement shown to be particularly suitable. This is done using a multifilter technique used that uses additional wavelength ranges and evaluates the absorption of the pulp-specific resonance frequency, so that the sensor measures water weight and fiber weight at the same time. The measurement enables a direct display at a

Measuring range from 0 - 40% for the absolute

2 moisture content. From about 80 to 100 g / m paper weight, only the surface moisture is measured.

To measure the exact same profile points, the sensors are arranged opposite each other above and below the web.

A device for carrying out the method according to the invention is set out in claim 6 and preferred embodiments are specified in subclaims 7 to 11.

A breaker bar is arranged between two guide rollers spaced apart from one another, which serve to support the passing web. The breaker bar has a round rod provided with a rotary drive and can be moved with the round rod first into the intermediate space which is formed by two guide rollers spaced apart from one another. For this purpose, means are provided for repetitively setting positions perpendicular to the running direction of the web.

The two guide rollers interacting with the crusher line are advantageously arranged such that the web guide does not change before and after the guide rollers, regardless of the position of the Breaker bar takes between the guide rollers. The web surface to be printed, which is supported against the guide rollers, is protected in that the peripheral speed of the guide rollers is synchronized with the web speed by means of its own drive.

The smaller the distance between the axes of the two guide rollers, the greater the depth of immersion of the crusher line affects a relatively larger wrap angle of the web over the round bar. For geometric reasons, the center distance of the guide rollers is at least 1.2 times larger than their outer diameter.

In a particularly preferred embodiment of the invention, the diameter of the round rod is at least 40 times smaller than the diameter of the guide rollers. With the selected geometry, there is already an influence on the curvature of the web with a small immersion depth of the round rod, with the advantage that a sufficient adjustment range of the breaker bar with respect to the curvature is available without a significant loss in bending stiffness of the web, as occurs in the example 2 and 3 is shown. Another advantage of the selected geometry results in an almost linear relationship between the immersion depth and the wrapping of the web over the round bar.

In a further embodiment of the invention, the breaker bar has a slidable material Manufactured receptacle for supporting and guiding the round bar. The receptacle, which preferably extends over the entire width of the web, supports the round rod rotating in it uniformly without the round rod being able to bend.

A further embodiment of the invention has a groove in the longitudinal direction in the bottom of the receptacle, that is to say across the entire width of the web, which is provided with at least one cooling water inlet and outlet channel at its ends. The rotating round bar rests on the groove and is constantly wetted by cooling water which is passed through the groove. At the same time, particles adhering to the round rod and torn from the web are removed.

If, on the other hand, it is a sheet with a dense underlay side closed by pigmentation or gluing or a sheet underlay which is very sensitive to moisture, in another preferred embodiment of the invention it is possible to pass the cooling water through the round rod consisting of a thick-walled tube.

Example 1 :

Implementation of the method in a board machine using a device according to the invention, as shown in FIG. The starting material was a 3-ply cardboard made from waste paper with a 3-ply top layer. The cardboard web had the following measured values in the cardboard machine before winding on :

Web width: 3.65 m

Web speed: 450 m / min basis weight incl.

Line application: 220 g / m ²

Total moisture: 8.5 to 9%

Surface moisture ceiling: 9.4% Surface moisture underlay: 6.6%

The measured absolute moisture content of the cardboard web corresponds to the respective mean values, which were taken from the measuring positions, driver's side, middle and drive side on the cardboard machine.

Information about the device according to the invention.

Round bar: - diameter 10 mm

- Speed 40 rpm, direction of rotation the same

Web direction

- Water cooling (inlet temperature 15 ° C

Outlet temperature 18 ° C.

Guide rollers: - diameter 500 mm

- Center distance 640 mm

- Circumferential speed synchronized with web speed

Setting range of the

Round bars: from 0 mm without web contact to 150 mm max. Immersion depth T The board machine produced at almost max. Drying performance, with the setting of the steam pressures of the upper drying cylinders to the lower drying cylinders at 3.5 bar almost the same and at a high level.

The target laboratory curvature of + 3 mm, controlled after standstill, transition and demolition, resulted in an immersion depth T of the round bar of 12 cm under given conditions.

The difference in surface moisture changed, the surface moisture on the top side always being higher than that on the underside, by more than 0.5 percentage points, e.g. if it increased, the round rod had to dip 1 cm deeper into the underside of the web. Given the geometry, this resulted in an increase in the wrap angle (2 × α) of the web over the round bar of approximately 4 degrees.

With this regulation, the curvature could be kept stable over a period of more than 3 hours. On the basis of trend calculations, moisture-independent influences on the curvature are caused by changes in the setpoint value of the control loop, i.e. Adjustment of the average surface moisture difference in relation to the immersion depth T, compensated at intervals of 2 to 3 hours.

Example 2:

Tests with the device mentioned in Example 1, as shown in FIG. 1, did not result in any noteworthy Changes in the bending stiffness of the tested sheet materials up to an immersion depth of 15 cm. The web materials examined were single and multilayer cartons of

230 to 425 g / m. The diagram shows the influence of the

Flexural rigidity of the sheet materials, expressed as the geometric mean of the root from longitudinal and transverse measurements (L x q), to the immersion depth of the round bar.

Example 3:

In Figure 2, the curvature is given in mm, where (minus) indicates a rolling of the A4 sheet to the ceiling and (plus) a rolling to the base. The immersion depth of the round bar, as in the previous examples, is given in cm.

The entered lines show the influence of the curvature on the immersion depth of the round bar. It becomes clear that above an immersion depth of 15 cm, the curvature above the max. permissible value of + 10 mm. Accordingly, a greater immersion depth of the round bar in the underside of the web was not required to correct the flatness for the given web materials, i.e. in connection with example 2 it has been shown that there was no influence of the bending stiffness in the setting range of the immersion stiffness of the round bar.

The following figures serve to explain the invention in more detail. Show it: Figure 1 and 2 diagrams of the in Examples 2 and

3 described effect of the immersion depth of the guide element on the curvature and bending stiffness;

Figure 3 shows the effect of the immersion depth of the breaker bar on the wrap angle of the web for a particular geometry.

FIG. 4 shows the side view of a device according to the invention in a schematic representation, arranged in a cardboard machine, and the operating sequence of the control circuit according to the invention;

FIG. 5 shows a front view in partial section of the one in FIG

4 shown detail IV, shown over the working width of the board machine;

FIGS. 6 and 7 in an enlarged isometric representation of parts of the receptacle with round rods mounted therein, FIG. 6 shows the section V shown in FIG. 5.

FIG. 4 shows schematically the guidance of the cardboard web (9) in reverse from the winding system (21) of a cardboard machine. Immediately in front of the winding system (21) there is a surface moisture measuring device with an infrared reflection sensor (7) for the ceiling and another infrared reflection sensor (8) for the underside of the cardboard web (9). These sensors are installed, preferably with further sensors, as are customary today in the quality control system, in a measuring frame (22) which may be constructed with a traversing device. On the right-hand side of FIG. 4 is the device for mechanically correcting flatness faults arranged in the machine frame (1). The breaker bar (3), which is displaceably mounted by linear guides (28) perpendicular to the web running direction (2), is shown in two positions. The lower, dash-dotted position shows with the lifting cylinder (12) completely lowered that the cardboard web (9) has no contact with the breaker bar (3) and the guide rollers (5; 6). The second position corresponds to a possible position of the breaker bar (3) with the immersion depth T, the cardboard web (9) being subject to a three-fold change in direction. For a given working width, that is to say the maximum web width of the cardboard machine of 3.65 m, the guide rollers (5; 6) have, for example, an outer diameter D of 500 mm and their center distance is 640 mm. This results in a narrow intermediate space (10) in which the crusher bar (3) can be moved into the center. The wrap angle (2 x α) of the cardboard web (9) over the crusher line (3) increases approximately proportionally with increasing immersion depth T according to FIG. 3, where α the angle of the cardboard web (9) from the guide roller (6) to the web running direction (2 ) indicates.

The measurement signal processing takes place in the transmission element

(Ü) instead. The connections of the signal transmission are shown by dashed lines. The other

Surface moisture measurement of the infrared reflection sensors (7; 8) determined

Difference value x results in the control actual value. The in

Transmission link (ü) by non-moisture-dependent Disturbance variables Z. adjusted and from the deviation of the

Target laboratory curvature in correlation to x derived e1

The manipulated variable x results in the set immersion depth T of the breaker bar (3). The current position x _ of the breaker bar (3) is indicated by the position indicator (11).

The two guide rollers (5; 6) each have a drive (20) rotating synchronously with the web speed, so that there is no line damage on the cover of the cardboard web (9).

Figures 5 and 6 show the upper part of the

Breaker bar (3) over the working width (AB) of the

Cardboard machine with the stored on it and by means of

Rotary drive (13) coupled round rod (4). The

Round rod (4) has a diameter d of 10 mm in relation to the aforementioned example, i.e. 50 times smaller than the diameter D of the opposite one

Guide rollers (5; 6). The receptacle (14) made of cast iron, for example, guides the round rod (4) in a 10 mm wide and 5 mm deep groove made by milling or broaching. In the middle of the bottom of the groove is a second groove (17) with a width and

Depth of 5 mm. The hard chrome-plated and polished round rod (4) is supported on the slightly broken or rounded edges (24) of the groove (17) and is supported on the end faces of the receptacle (14) by a known bearing (15) and

Loεlager (16) held, which simultaneously seal the receptacle end. The groove (17) made on the groove bottom serves to cool the round rod

(4), in the cold well water 15 ° C on the The driver side is fed through channel (18) and extracted on the drive side through channel (19). Sucking off the cooling water prevents the channel (19) from becoming blocked by stripped fibers.

If, on the other hand, as shown in FIG. 7, a thick-walled tube is used as a round rod (25), the cooling water can be supplied and removed at the ends by rotating unions. The rotary drive of the round rod (25) must then be arranged laterally and the round rod (25) is driven, for example, by means of a toothed belt drive.

Claims

Process for eliminating flatness problems in the production of webs, in particular cardboard webs with grammages of more than 200 g / m in cardboard machines, wherein a guide element arranged in front of the winding and transversely to the running direction of the web in connection with two spaced-apart guide rollers which run in the running direction seen the web, before and after the guide element, cause a three-fold change in direction of the web, characterized in that a guide element shaped as a round rod and rotated by means of a rotary drive acts on the underside of the web perpendicular to the web running direction, in such a way that to regulate the flatness of a cardboard web the manipulated variable for the depth of immersion of the guide element in the underside of the web is derived from the difference between the continuously or intermittently measured surface moisture of the current top and bottom of the web, so that when the surface moisture difference changes, the immersion depth of the line elements, which is indicated by position sensors, accordingly is adjusted.

2. The method according to Anεpruch 1, characterized in that daε guide element in the running direction of the web with a circumferential speed that is <1% of the web speed, rotates with or in opposite directions.

3. The method according to any one of claims 1 and 2, characterized in that the guide element is cooled.

4. The method according to any one of claims 1 to 3, characterized in that the

Surface moisture measurement is carried out by means of two mutually opposite infrared reflection sensors.

5. The method according to any one of claims 1 to, characterized in that the monitoring of the immersion depth of the guide element is carried out by means of displacement transducers.

Device for the mechanical elimination of

Flatness problems for board machines with an im

Machine frame (1) arranged transversely to

Machine direction oriented and vertically movably mounted breaker bar (3) with a thin round rod (4) mounted on it, which serves as a sliding surface, characterized in that the breaker bar (3) between two spaced guide rollers (5; 6) which for

Support of the passing train (9) serve, is arranged, and that the breaker bar (3) with the round rod (4; 25) in the space (10) of the guide rollers (5; 6) is movable, the breaker bar (3) means (11) for repeatable adjustment from positions perpendicular to the running direction of the web (9) and that the round bar (4; 25) is also provided with a rotary drive (13) which sets the round bar (4; 25) in rotation during web contact.

7. The device according to claim 7, characterized in that the round rod (4; 25) has a diameter d which is at least 40 times smaller than the diameter D of one of the opposite guide rollers (5; 6) iεt.

8. Device according to one of claims 6 and 7, characterized in that the breaker bar (3) has a receptacle (14) made of slidable material for supporting and guiding the round bar (4; 25) and that the round bar (4; 25) is held on the end faces of the breaker bar (3) by means of bearings known per se.

9. Device according to one of claims 6 to 8, characterized in that in the longitudinal direction in the bottom of the receptacle (14) a groove (17) with supply and discharge channels (18; 19) for cooling water is arranged.

10. Device according to one of claims 6 biε 8, characterized in that the round rod (25) consists of a thick-walled tube and has rotary unions at its two ends, which are connected to a cooling water circuit.

11. Device according to one of claims 6 to 10, characterized in that the surface of the Rundstabeε (4; 25) is hard chrome-plated and polished iεt.